This invention relates generally to rotating machinery, and particularly to gas turbine engines that are subject to axial thrust loads. More particularly, the present invention relates to a thrust compensation apparatus for rotating machinery that utilizes an electromagnetic thrust disk aided by pressure thereacross to counteract axial thrust loads. Although, the present invention was developed for use in a gas turbine engine, certain applications may be outside of this field.
It is well known that a gas turbine engine integrates a compressor and a turbine having components that rotate at extremely high speeds in a high temperature environment. One component being a rotor disk that carries a row of airfoils utilized to influence the gaseous flow within the engine. The rotating components typically cooperate with a rotatable shaft and are supported by radial and thrust bearings that must withstand significant dynamic and static loads within a hostile environment. During operation of the gas turbine engine the bearings are subjected to forces including: shock loadsxe2x80x94such as from landings; maneuver loadsxe2x80x94associated with sudden change in direction, and centrifugal forces attendant with the rotating components.
As engine designers continue to increase the efficiency and power output from gas turbine engines the application of magnetic bearings for supporting and controlling the rotor and rotatable shaft becomes desirable. The integration of magnetic bearings into the engine would allow the rotor shaft to be supported by magnetic forces, eliminate frictional forces, along with mechanical wear and the lubrication system.
A magnetic thrust bearing includes a magnetic flux field and a rotatable thrust disk that is acted upon by the magnetic flux field. The application of magnetic bearings in flightweight gas turbine engines requires a compactness of bearing design, which ultimately equates to lighter weight. The capacity of electromagnetic bearings to carry axial thrust loads is generally limited by the size of the thrust disk. Rotating machinery that operate at high speeds may require magnetic bearings so large as to be impractical, if not impossible, to implement. Thus, as a result of this limitation on the thrust capacity of electromagnetic bearings, a conventional thrust balance piston is often incorporated into the rotor system of high-speed machinery.
Although the prior techniques utilizing magnetic thrust bearings for gas turbine engines are steps in the right direction, the need for additional improvements still remains. The present invention satisfies the need in a novel and unobvious way.
One aspect of the invention described herein accomplishes a reduction in axial thrust loads in a high-speed machine by utilizing an electromagnetic thrust bearing having a pressure differential across the electromagnetic thrust disk to gain additional thrust capacity.
One form of the present invention contemplates a gas turbine engine having an electromagnetic thrust bearing located within the engine. The thrust bearing comprises a thrust disk mounted on a shaft of a rotor system, and a thrust bearing stator coupled to a support frame. A pressurized fluid is provided to one side of the electromagnetic thrust bearing. Seals are formed integral with the thrust disk rotor to create a higher-pressure chamber on one side of the thrust bearing and a lower pressure chamber on the other side of the thrust bearing. The pressure differential across the thrust bearing augments the electromagnetic attractive force between the thrust rotor and thrust stator to counter the axial thrust load.
Another form of the present invention contemplates the use of mechanically attached seals on the thrust disk rotor.
One object of the present invention is to provide a unique electromagnetic thrust bearing system.
Related objects and advantages of the present invention will be apparent from the following description.